Display devices are generally required to have as wide a viewing angle as possible so that a clear image can be seen from any angle. Various technological developments have been carried out in connection with widening of the viewing angle of liquid crystal display devices. This is particularly because liquid crystal display devices, which have been in widespread use in recent years, include liquid crystal having viewing angle dependence.
However, a narrow viewing angle may be preferable, in a specific use environment. This allows a display content to be visible only to the user. Furthermore, electronic devices such as laptop personal computers, personal data assistants (PDAs), and portable phones are particularly likely to be used in sites, where the general public may be present, such as in trains and airplanes. In such a use environment, the display device has preferably a narrow viewing angle because it is undesirable to let other people nearby see a display content, in light of reason such as confidentiality protection or privacy protection. As described above, there have been increasing demands in recent years for the ability to switch a viewing angle of a single display device between a wide viewing angle and a narrow viewing angle, in conformity with a use condition. Note that the demands are shared by any display devices, not limited to liquid crystal display devices.
In order to address such demands, Patent Document 1, for example, suggests an arrangement in which a retardation controlling device and a display device for displaying an image are provided and a viewing angle characteristic is changed by controlling a voltage applied to the retardation controlling device. According to Patent Document 1, the liquid crystal used in the retardation controlling liquid crystal display device is exemplified by a chiral nematic liquid crystal, a homogeneous liquid crystal, a randomly aligned nematic liquid crystal, and the like.
Further, Patent Documents 2 and 3, for example, disclose arrangements in which a viewing angle controlling liquid crystal panel is provided above a liquid crystal display panel, these panels are sandwiched by two polarizing plates, and a voltage applied to the viewing angle controlling liquid crystal panel is adjusted so that a viewing angle is controlled. According to Patent Document 2, the liquid crystal of the viewing angle controlling liquid crystal panel is a twisted nematic liquid crystal.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 174489/1999 (Tokukaihei 11-174489; published on Jul. 2, 1999)    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 268251/1998 (Tokukaihei 10-268251; published on Oct. 9, 1998)    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 309020/2005 (Tokukai 2005-309020; published on Nov. 4, 2005)
According to the Patent Document 1, the provision of the retardation controlling liquid crystal device allows switching between a wide viewing angle mode and a narrow viewing angle mode. However, this does not give rise to sufficient effect. For example, Patent Document 1 shows an equal-contrast curve for a contrast ratio of 10:1, as shown in FIG. 20. This shows that the contrast in a wide viewing angle direction is surely decreased in the narrow viewing angle mode. However, a decrease in contrast to such a degree causes a display to be sufficiently visible to a person next to the user. This is because a display is in general sufficiently visible even if the contrast ratio is decreased, for example, to 2:1.
According to the arts disclosed in Patent Documents 2 and 3, switching between a wide viewing angle and a narrow viewing angle is carried out by changing the voltage applied to the viewing angle controlling liquid crystal panel so that the contrast is adjusted. However, this does not give rise to sufficient effect, either. For example, (a) through (c) of FIG. 21, show viewing angle distributions in the wide viewing angle mode. (a) through (c) of FIG. 22 show viewing angle distributions in the narrow viewing angle mode.
Namely, all of the arts disclosed in Patent Documents 1, 2, and 3 adopt a method in which the switching between a wide viewing angle mode and a narrow viewing angle mode is carried out by decreasing the contrast in the wide viewing angle direction. However, according to such a method, blocking off of a view in the narrow viewing angle mode is not sufficient in the wide viewing angle direction, i.e., in a direction in which the narrow viewing angle is not realized. This is likely to cause a problem that a display may be seen by other people.
The present technology addresses the problem discussed above, and aims to provide a liquid crystal display which is capable of enhancing effect of narrowing a viewing angle.
In order to solve the above problem, a liquid crystal display of an example embodiment presented herein includes: a backlight; a display panel; a viewing angle control panel for controlling a viewing angle of the display panel; and a lens sheet provided either (i) between the backlight and the display panel which is provided so as to be closer to the backlight than to the viewing angle control panel, or (ii) between the backlight and the viewing angle control panel which is provided so as to be closer to the backlight than to the display panel.
According to the above embodiment, a lens sheet is provided either (i) between the backlight and the display panel which is provided so as to be closer to the backlight than to the viewing angle control panel, or (ii) between the backlight and the viewing angle control panel which is provided so as to be closer to the backlight than to the display panel. This allows the lens sheet to collect light emitted from the backlight, so that the viewing angle of the liquid crystal display can be narrowed.
As a result, it is possible to provide a liquid crystal display which is capable of better narrowing a viewing angle.
In order to solve the above problem, a liquid crystal display of the present embodiment includes: a backlight; a display panel; a viewing angle control panel for controlling a viewing angle of the display panel; and a plurality of layered lens sheets provided either (i) between the backlight and the display panel which is provided so as to be closer to the backlight than to the viewing angle control panel, or (ii) between the backlight and the viewing angle control panel which is provided so as to be closer to the backlight than to the display panel.
The plurality of layered lens sheets is capable of collecting light emitted from the backlight more closely than a signal lens sheet.
The liquid crystal display may be arranged such that the plurality of layered lens sheets are made up of a first lens sheet and a second lens sheet, the first lens sheet being provided so as to be closer to the backlight and having a prism ridgeline pattern which is vertically stripped with respect to the display panel, and the second lens sheet being provided on the first lens sheet and having a prism ridgeline pattern which is horizontally stripped with respect to the display panel.
This allows the first lens sheet having a vertically-stripped prism ridgeline pattern to collect light emitted from the backlight so that the viewing angle can be narrowed in the horizontal direction. The above arrangement further allows the second lens sheet having a horizontally-stripped prism ridge pattern to collect light emitted from the backlight so that the viewing angle can be narrowed in the vertical direction.
As a result, it is possible to efficiently narrow the viewing angle both in the horizontal and vertical directions with the use of the first and second lens sheets.
The liquid crystal display may be arranged such that each of the display panel and the viewing angle control panel includes a liquid crystal cell, the liquid crystal display, further including: at least one polarizing plate, which has not been subjected to a diffusion treatment, provided between the liquid crystal cell of the display panel and the liquid crystal cell of the viewing angle control panel.
Since at least one polarizing plate, which has not been subjected to a diffusion treatment, is provided between the respective liquid crystal cells of the display panel and the viewing angle control panel, narrowing of a viewing angle is not inhibited. In other words, for example, if a polarizing plate, which has been subjected to a diffusion treatment, is provided between the respective liquid crystal cells of the display panel and the viewing angle control panel, narrowing of a viewing angle is inhibited.
The liquid crystal display may preferably be arranged such that the viewing angle control panel includes: a liquid crystal cell; and a driving circuit for applying a voltage to the liquid crystal layer, the liquid crystal cell including: a pair of light-transmitting substrates; and a liquid crystal layer, provided between the light-transmitting substrates, in which liquid crystal molecules are aligned vertically, and the liquid crystal cell being provided between two polarizing plates which face each other so that polarizing transmission axes are substantially orthogonal to each other, and the driving circuit changing an alignment of the liquid crystal molecules in the liquid crystal layer of the liquid crystal cell so that a display state is switched between a first viewing angle range and a second viewing angle range which is within the first viewing angle range and is narrower than the first viewing angle range.
According to the above embodiment, two polarizing plates having polarizing transmission axes which are substantially orthogonal to each other are provided so as to sandwich the liquid crystal cell of the viewing angle control panel. The liquid crystal cell and the two polarizing plates are not necessarily in contact with each other. There may be another element between the liquid crystal cell and the two polarizing plates.
According to the above arrangement, the polarization of light to be emitted from the liquid crystal cell of the viewing angle control panel is changed due to birefringence which is caused by the liquid crystal when the alignment of the liquid crystal molecules is changed while a predetermined voltage applied to the liquid crystal layer. As a result, it is possible to, depending on the angle, transmit or block the light to be emitted from the viewing angle control panel toward a viewer, while the polarizing plate provided on a side of the viewing angle control panel which side faces the viewer serves as an analyzer. In other words, the display mode can be switched between (i) a wide viewing angle mode which provides the first viewing angle range and (ii) a narrow viewing angle mode which provides the second viewing angle range, which is within the first viewing angle range and narrower than the first viewing angle range. Note that the terms “wide viewing angle” and “narrow viewing angle” do not refer to any specific, absolute angle ranges. They refer to a relatively wide viewing angle and a relatively narrow viewing angle, respectively.
Further, according to the above arrangement, the use of the liquid crystal cell having liquid crystal molecules aligned vertically allows the narrow viewing angle mode to be achieved in which mode a display is visible from within a limited viewing angle. Consequently, unlike the conventional art of controlling a viewing angle in which art the contrast of a display in the wide viewing angle direction is decreased, the viewing angle can be controlled by switching between transmitting of light and blocking of light. As a result, the liquid crystal display is capable of better narrowing a viewing angle in the narrow viewing angle mode.
In order to solve the above problem, a liquid crystal display of the present embodiment includes: a backlight; a display panel; and a viewing angle control panel for controlling a viewing angle of the display panel, each of the display panel and the viewing angle control panel including a liquid crystal cell, the liquid crystal display, further including: at least one polarizing plate, which has not been subjected to a diffusion treatment, provided between the liquid crystal cell of the display panel and the liquid crystal cell of the viewing angle control panel.
According to the above embodiment, the liquid crystal display includes a backlight, a display panel, and a viewing angle control panel for controlling a viewing angle of the display panel.
Further, each of the display panel and the viewing angle control panel includes a liquid crystal cell, and at least one polarizing plate, which has not been subjected to a diffusion treatment, is provided between the respective liquid crystal cells of the display panel and the viewing angle control panel. Thus, even if a lens sheet is not provided, the liquid crystal display simply having the above arrangement is capable of better narrowing a viewing angle.
For a fuller understanding of the nature and advantages of the example embodiments presented herein, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.